Nafion-assisted n-TOPCon bottom cells integrated with FAPbI₃ perovskite top cells for high-efficiency four-terminal tandem solar cell under rear-albedo illumination

Perovskite/silicon tandem photovoltaics offer a compelling pathway to surpass the efficiency limits of single-junction silicon. However, perimeter-induced recombination and shunting in n-type TOPCon bottom cells remain a critical barrier to achieving high tandem performance. Here, we present a simple and scalable Nafion-based edge-engineering approach designed to selectively passivate the damaged wafer perimeter without altering the poly-Si/SiOₓ contact. The ionomer forms a stable ionic barrier that suppresses edge-related recombination, thereby improving carrier collection in the bottom sub-cell. As a result, the Nafion-passivated n-type TOPCon cells achieved a power conversion efficiency (PCE) of 23.37%, with reduced series resistance and enhanced external quantum efficiency (EQE) across the visible and near-infrared range. Integration with a high-performance nip-structured FAPbI₃ perovskite top cell (23.62%) enables the four-terminal (4 T) tandem configuration to reach a combined PCE of 30.01% under a bifacial operation with a rear albedo of 0.3 sun. Furthermore, PVsyst simulations at the system level indicate a high-performance ratio of 0.859, highlighting substantial energy-yield potential and supporting the practical viability of this tandem architecture for large-scale deployment.